I saw this on Drudge:

A Japanese airline has started asking passengers to go to the toilet before boarding in a bid to reduce carbon emissions.

All Nippon Airways (ANA) claims that empty bladders mean lighter passengers, a lighter aircraft and thus lower fuel use.

It won't be long now before some airline works this idea into its fee structure. Perhaps a $5 fee for people who don't go #1 before boarding, a $10 fee for people who don't go #2 before boarding, and $15 fee for people who do neither.